Nickel (Ni) is a ubiquitous occupational and environmental pollutant, which has been widely used in the Ù½eOd of industry, such as battery production, catalyst, electroplating, pigments, and alloys. Excessive Ni and its compounds can pass through blood-testis barrier and cause adverse eوٴects in male reproductive system, mainly presenting as testicular injury, abnormal spermatozoa development, cell apoptosis, steroidogenesis disorder, oxidative stress and the generation of reactive oxygen species (ROS) [1-3]. Recently, with the development of nanotechnology, the application of nano-selenium (Nano-Se) has attracted the worldwide interests of researchers due to its higher biological eوٴects and lower toxicity than other selenocompounds [4]. Furthermore, the fact that Nano-Se possesses higher antioxidant ability led us to hypothesize that Nano-Se might attenuate Ni-induced oxidative damage in testes. To verify this possibility, male Sprague-Dawley rats were treated with nickel sulfate intraperitoneally in the absence and presence of various concentrations of Nano-Se given by oral gavage. As expected, Nano-Se ameliorated testicular damages caused by Ni, such as irregular seminiferous tubules, loss of spermatogenesis, degeneration and necrosis of germ cells, along with which the indicators of oxidative stress in testes were changed. Our data suggested that Nano-Seco-treatment sLJQLÙ½cDQtO\ decreased the levels of MDA and 8-OHdG and elevated the GPx activity, clearly indicating that Nano-Se can protect testes from Ni-induced oxidative injury.